The present disclosure relates to a screw-type solid-bowl centrifuge including a rotatable drum having a tapering portion and a cylindrical portion. The rotatable screw includes a screw body, at least one main screw blade surrounding the screw body and forming a plurality of screw flights. The plurality of screw flights forms a conveying path configured to transport a material to be processed in the centrifuge. Two blade segments are arranged in the conveying path in portions of the plurality of screw flights. The at least one main screw blade is provided in a region of the blade segments that includes clearances configured to allow a throughflow of the material to be processed to flow between adjacent screw flights.
Decanter screws are known from the prior art, in which clearances are provided in the screw blade, as, for example, from DE 41 32 693 A1. Moreover, it is also known to form screw flights resembling blade segments, as, for example, from WO 97/23295. These blade segments, however, sometimes extend well into the conical portion, this being a disadvantage. Furthermore, they are distributed on the circumference of the screw body in the entire region of the latter, and this has likewise proved to be somewhat of a disadvantage. Moreover, additional blade segments are not, for example, set up in the conveying path between the screw flights, but, instead, the blade segments themselves form the screw flights. By the two references just mentioned above, a sufficiently high efficiency in the extraction of olive oil, for example, cannot be achieved.
One method appropriate in the extraction of olive oil is known from EP 0 557 758. In this method, two-phase separation is carried out, in which the oil is separated directly from a solid/water mixture.
The efficiency of known methods is improved, for example, by WO 02/38 278 A1, which discloses, in addition to generic features, that additional blade segments are arranged in the conveying path in portions between adjacent screw flights. The screw blade is provided in the region of the screw blade segments with clearances which are formed in such a way that a throughflow of the centrifuged stock between adjacent screw flights is possible.
Other prior art includes WO97/22411 A1, WO 2005/084814 A1, DE 699 20 500 T2 and EP 0 845 296 A.
Proceeding from WO 02/38 278 A1, the present disclosure relates to a decanter screw to improve a processing of pulps, for example, oil extraction, by a decanter having a screw as disclosed herein.
Thus, the present disclosure relates to a screw-type solid-bowl centrifuge comprising a rotatable drum including a tapering portion and a cylindrical portion. The rotatable screw includes a screw body, at least one main screw blade surrounding the screw body and forming a plurality of screw flights. The plurality of screw flights forms a conveying path configured to transport a material to be processed in the centrifuge. Two blade segments are arranged in the conveying path in portions of the plurality of screw flights. The at least one main screw blade is provided in a region of the blade segments that includes clearances configured to allow a throughflow of the material to be processed to flow between adjacent screw flights of the plurality of screw flights. The two blade segments are further arranged in only a first and a second of the plurality of screw flights. A first of the two blade segments in the first screw flight lies nearer the tapering portion than the second screw flight. The first of the two blade segments is configured to be turned forward in relation to the at least one main screw blade. A second of the two blade segments in the second screw flight located in a direction axially further away from the tapering portion than the first screw flight is formed in a plane substantially parallel to a plane of the at least one main screw blade.
Consequently, a careful inflow of the product or material to be processed is carried out via at least one screw flight. As noted above, in a first screw flight, which lies nearer in the direction of a tapering portion than the other screw flights with the blade segments, the blade segments are oriented so as to be turned forward in relation to the main screw blade. The further blade segments in the next screw flight directly following axially away from the tapering portion are formed or oriented parallel to the main screw blade.
The blade segments are arranged in the conveying path in only two screw flights. In a first of the two screw flights which lies nearer in the direction of a tapering portion than the other of the two screw flights, part of the blade segments are oriented so as to be turned forward in relation to the main screw blade. A further part of the blade segments in the next screw flight directly following axially away from the tapering portion are formed parallel to the main screw blade.
Additionally the tapering region of the screw has arranged in it, in the screw flight, an auxiliary screw blade which extends over the entire tapering region of the screw.
The present disclosure also relates to a damming device arranged in a transitional region between the cylindrical portion and the conical or tapering region.
In accordance with the present disclosure, an output of the centrifuge can be increased by approximately 20%. That is, from 5 t/h to 6 t/h.
The oil yield from the centrifuge, according to the present disclosure, is increased by approximately 10%.
The solid phase can be set, for example, at a residual moisture content of approximately 40% to 55%. It is thereby possible to meet the essential requirements as to a residual moisture content, even as a function of the respective provisions to be adhered to.
By the screw or centrifuge, according to the present disclosure, the two-phase oil extraction, and also the three-phase oil extraction still occasionally used, can be improved. In the latter case, the oil is separated as a liquid phase in a three-phase separating cut from a second phase, essentially from water, and from a third phase, essentially from solids.
According to the present disclosure, by a combination of clearances and of “intermediate blade segments” in the conveying path on only two screw flights, the efficiency of various centrifugal separating processes in three-phase separation can surprisingly be markedly increased further, as compared with the prior art. That is because an acceleration of the solid, both in the circumferential direction and in the axial direction, is achieved. This entails be ter phase separation of the viscoelastic and compressible paste. This prevents the situation where the inflowing paste, immediately after flowing in, is compacted when it impinges onto the solid in the rotor.
In accordance with the present disclosure, the screw can also be retrofitted easily in existing centrifuges.
The screw, according to the present disclosure, is suitable for use in a method for oil extraction from fruits and seeds and for the better dewatering and/or deoiling of mashes including organic materials, for example seed mashes, pod mash, animal tissue, such as fish, protein, and fatty tissue cells. Moreover, the situation is prevented where the inflowing paste, immediately after flowing in, is compacted when it impinges onto the solid in the rotor.
The screw, according to the present disclosure, is also suitable for the dewatering of other compressible pulps. For example, the dewatering is applicable in wine production.
The clearances in the screw blades are designed in such a way that they project radially at least into the region of the solid zone. For example, 70-95%, or 70-100%, of the screw blade height.
The height of the blade segments is approximately 0-30% lower than the screw blade height.
The blade segments are designed as rectangular plates. The plates may be trapezoidal or have rounded elements and/or elements shaped so as to taper or broaden outward from the screw body.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.
The present disclosure also includes drawings, further described below.